my thoughts on this is that SE currently locked the job because it is only partially ready. BLU takes a massive amount of time to convert the massive amount of monster data in the game to create learnable abilities for them all. By limiting it and then slowly advancing the job, they can take the time to do it right and not break something. My guess is Beastmaster will be the next limited job due to the same reason. they have to convert monster data and that just takes time to do. Once BLU is caught up, they can add it to be playable in all the other content. But who knows exactly how fast SE is planning to advance BLU. they only told us they will advance the level cap with each patch release. But does it get 10 levels each time or 5? at 10 levels, it would take 3 patch cycles to get caught up. Meaning at 5.2 it would be level 70.